Research Progress of Acupuncture Analgesia for Labor

Liu Xiao-hui, Wu Ling-ling, Yi Wei

1 Guangzhou University of Traditional Chinese Medicine, Guangdong 510405, China

2 Third Hospital Affiliated to Sun Yat-sen University, Guangdong 510000, China

Research Progress of Acupuncture Analgesia for Labor

Liu Xiao-hui, Wu Ling-ling, Yi Wei

1 Guangzhou University of Traditional Chinese Medicine, Guangdong 510405, China

2 Third Hospital Affiliated to Sun Yat-sen University, Guangdong 510000, China

Labor pain is a kind of severe pain the lying-in women of natural childbirth must undergo. The labor quality is decided by the tolerance to pain. Acupuncture analgesia for labor pain has been increasingly concerned and applied by more and more clinical workers because of its safety and efficacy. By summarizing and analyzing the choice and applications of various factors of acupuncture analgesia for labor pain such as acupoint selection, instrument analgesic coefficient, and the needling techniques in acupuncture analgesia for labor pain in the recent 12 years, this study aims to provide a theoretical foundation for the clinical application of acupuncture analgesia for labor pain.

Acupuncture Therapy; Electroacupuncture; Acupuncture Analgesia; Labor Pain; Review

Childbirth is a process that the fetus and placenta are completely discharged from the uterus in pregnancy of 28 weeks and above[1]. In the medical pain indexes, labor pain is just second to the burning pain. Labor pain exists in the whole process of childbirth. With the social progress, people demand higher medical conditions and qualities increasingly. Because of its greater influence on the psychology and pathology of the lying-in women, labor pain has been more and more emphasized by the clinicians and lying-in women. The labor quality is decided by the tolerance to pain. Due to crying of labor pain, the lying-in women may have hyperventilation, increased consumption of oxygen, so as to induce respiratory alkalosis, affecting the oxygen supply to the placenta, and hence causing hypoxemia in the fetus and maternal and even fetal distress. Therefore, in order to enhance the perinatal quality, and reduce the sufferings of the lying-in women, labor analgesia has been increasingly and extensively concerned. Currently, because of its safety and efficacy, acupuncture analgesia for labor pain has been acknowledged by majority of the clinicians and has been widely applied clinically. But, the acupoints, instrument analgesic coefficient, and the needling manipulations are in lack of standard. Now, for the above-mentioned issues, the summary will be given in the following, based upon the literature of the recent 12 years on acupuncture analgesia for labor pain.

1 Acupoint Selection

In the ancient times in China, there was such a saying that “abortion is induced by puncturing Sanyinjiao (SP 6) with the reducing technique and Hegu (LI 4) with the reinforcing technique.” This saying indicates that acupuncture had been extensively applied in labor in the ancient times.Wang LN, et al[2]reported in the review of 42 articles that the analgesic acupoints included body acupoints, ear acupoints and scalp acupuncture areas. There are 24 analgesic body acupoints, i.e. Hegu (LI 4), Houxi (SI 3), Lieque (LU 7), Neiguan (PC 6), Zusanli (ST 36), Shangliao (BL 31), Ciliao (BL 32), Dachangshu (BL 25), Guanyuanshu (BL 26), Shenshu (BL 23), Zhishi (BL 52), Kunlun (BL 60), Yanglingquan (GB 34), Zulinqi (GB 41), Sanyinjiao (SP 6), Yinlingquan (SP 9), Taichong (LR 3), Zhongji (CV 3), Guanyuan (GV 4), Qugu (CV 2), Huiyin (CV 1), Baihui (GV 20), and Zigong (EX-CA 1). In the ear acupoints, there are mainly Shenmen (TF4), Internal Genitalia (TF2), Sympathia (AH6a), Endocrine (CO18), and Subcortex (AT4). In the scalp acupuncture, mainly the Line 3 Lateral to Forehead [MS4, 1 cun long from the point 0.75 cun medial to Touwei (ST 8) straight downward] is selected. Although there are many analgesic acupoints for labor pain, the acupoints used in high frequency are comparatively concentrated, and mostly Hegu (LI 4), Sanyinjiao (SP 6), Zusanli (ST 36) or those three acupoints are selected as the major acupoints. In the above analgesic acupoints, the reports on Zusanli (ST 36) for stopping pain are maximum, with more profound studies[3]. Qin M, et al[4]believed that Zusanli (ST 36) had remarkable effect for stopping pain of the internal organs. Jin Y[5]believed that Zusanli (ST 36) could enhance the pain threshold, having better analgesic effect for visceralgia, body surface pain and cancer pain. By screening the relevant literature on acupuncture analgesia for labor pain in CNKI database from 2001-2012, acupuncture analgesia for labor pain was mentioned in 62 articles, in which Sanyinjiao (SP 6) was used in 25 articles, Hegu (LI 4) in 23 articles, Zusanli (ST 36) in 13 articles, Huiyin (CV 1) in 12 articles, Ciliao (BL 32) and Guanyuan (CV 4) in 6 articles respectively, Taichong (LR 3) was used in 5 articles, Qugu (CV 2) in 4 articles, Qihaishu (BL 24) in 3 articles, Guanyuanshu (BL 26), Dachangshu (BL 25) and Kunlun (BL 60) in 1 article, respectively. By the analysis of the literature on acupuncture analgesia for labor pain, it is found out that Sanyinjiao (SP 6) and Hegu (LI 4) were used most frequently, and Zusanli (ST 36) was the second.

2 Needling Techniques

There are numerous literatures on acupuncture analgesia for labor pain, but there are different reports on the needling techniques and time of needle retaining. Li L, et al[6]punctured bilateral Hegu (LI 4), Zusanli (ST 36), Sanyinjiao (SP 6) and Ciliao (BL 32) in acupuncture analgesia for labor pain, by the reducing technique. At the beginning of acupuncture, the acupoints were punctured first with light and medium stimulation for 30-40 min. In approaching to the late active period, the needles were manipulated with high intensity till the cervix opened fully, then needle in Ciliao (BL 32) was removed, and needles in other acupoints were retained or removed. Liu JY, et al[7]punctured Hegu (LI 4) for relieving labor pain. After routine disinfection, the needle was inserted for one inch and manipulated with the lifting-thrusting, twisting-rotating manipulations for arrival of the needling sensation, and then even reinforcing-reducing manipulations were done to guide the needling sensation upward to the upper arm. Tian JY[8]punctured bilateral Hegu (LI 4), when the cervix of the lying-in woman opened for 0.5-1 cm. After the arrival of the needling sensation, the needles were manipulated during each intermittent period of uterine contraction for intensifying the needling sensation. The needles were taken out after 25 min. In the later 20 min in puncturing Hegu (LI 4), bilateral Sanyinjiao (SP 6) and Kunlun (BL 60) were punctured. After the arrival of the needling sensation, the needles were manipulated during each intermittent period of uterine contraction, and the needles were taken out after 5-minute retention. Acupuncture was given in the first labor stage, once every two hours, till the cervix opened fully. Zang LN, et al[9]used ear point-embedding method plus acupuncture analgesia for labor pain. When the cervix of the lying-in women opened by 2 cm and the uterine contraction began intensified, the local skin of bilateral Hegu (LI 4) was disinfected, and the intradermal needle were clipped with the forceps to insert slightly into the acupoints, with the needle tip toward the heart, without painful sensation, and then the needles were fixed with plasters. The ear acupoints and Hegu (LI 4) were pressed every 3-5 min. The magnetic beads and intradermal needles were retained for 24 h after labor.

3 Coefficient of Electroacupuncture (EA)

Because EA has the acupuncture effect and also has the continuous stimulating effect of the current, its analgesic effect is appreciated by more and more medical practitioners. The coefficient of EA includes EA waveform, frequency, intensity and duration of stimulation, etc. In the study on acupuncture anesthesia and analgesia, most medical practitioners almost made the same choice on waveform and intensity of stimulation, selecting sparse-dense wave, with the intensity within the patient’s tolerance. But, there are different reports about the duration and frequency of stimulation.

3.1 Duration of stimulation

Usually it takes about 20-40 min for the body to elevate the pain threshold or pain tolerance threshold from the beginning of acupuncture to its maximum. The continuous manipulation of the needles or electric stimulation can maintain the analgesic effect to a higherlevel. After acupuncture, its pain threshold would come down with a curve of indexes, and the half-life period is about 16 min[10]. It has been proved by the animal experiments[11]that the analgesic effect would appear after the incubation period of 15 min and reach its peak at 45 min in the low frequency EA. If the duration of EA is limited within 30 min, it can produce an analgesic effect of dynorphin, and could not produce the effect of enkephalin and β-endorphin as the subjects for analgesia. Therefore, Fang JQ, et al[11]believed that in the treatment of various acute and chronic pains by EA, it was necessary to set the duration of stimulation at 45 min. But, on the contrary, Ye JH, et al[12]reported that at 15 min of EA, the content of Cyclic Guanosine Monophosphate (cGMP, similar to P-substance, participating in the transmission of harmful stimulation to the center) decreased, and the content of brain stem increased remarkblely at 45 min of EA, and cGMP content of the telencephalon decreased remarkably and the content of brain stem was slightly elevated at 30 min of EA, and the pain threshold was enhanced obviously. So, it is believed that 30 min is appropriate for acupuncture analgesia.

3.2 Frequency of stimulation

Sun RQ, et al[13]believed that the analgesic effect was better in the low-frequency EA than in the highfrequency EA. Li J, et al[14]also selected frequency of 2 Hz, 3.0 mA of current intensity, and 10 V of wave amplitude for EA. But, it has been proved in the studies by Ning Y and Jiang YX, et al[15-16], that the effect was obviously better in 100 Hz EA than in 2 Hz EA in relieving the joint tumefaction and pain in the rats with arthritis. This might be related to the specificity of the position of acupuncture frequency. It has been found out in the study on acupuncture analgesia for labor pain by Zhu L, et al[17]that EA of different frequencies could enhance the frequency of uterine contraction, but not significantly different, just significantly different in the intensity and power of the uterine contraction. The intensity and power of the uterine contraction were higher than those before acupuncture in 50 Hz group, and the intensity of the uterine contraction were lower than that before acupuncture in 2 Hz group and 20 Hz group, but without obvious difference in the contractive power. In 100 Hz group, the intensity of the uterine contraction and the contractive power were lower than those before acupuncture. When different frequencies were used on different acupoints, it was found out that EA on Hegu (LI 4) by 50 Hz could strengthen the contractive power, and by 100 Hz could inhibit the contractive power of the uterus. And EA on Sanyinjiao (SP 6) by 2 Hz, 20 Hz, or 50 Hz could also inhibit the contractive power of the uterus. The inhibitory effect by 50 Hz was the most obvious, but EA on Sanyinjiao (SP 6) by 100 Hz could intensify the contractive power. Therefore, it is pointed out that in the clinical application of Hegu (LI 4) and Sanyinjiao (SP 6) for promoting labor, if different frequencies were used for the two acupoints, 50 Hz should be chosen for EA on Hegu (LI 4), and 100 Hz should be chosen for EA on Sanyinjiao (SP 6); if same frequency was used for the two acupoints, 50 Hz is best for the effect.

4 Summary and Prospect

In the indexes of medical pains, labor pain ranks second only next to burning pain. With the change of medical mode and the enhancement of the life level, the females would bear higher expectation for the reproductive health and life quality. Safe and comfortable analgesic method for labor pain has always been the important issue concerned by the lying-in women and doctors. Currently, combined spinal-epidural anesthesia (CSEA) used in painless labor is remarkably effective, but all analgesic drugs would penetrate the placenta to a certain extent, and their adverse influence on the fetus could not be excluded, and side effects from analgesia by CSEA are gradually manifested. Therefore, higher level analgesic effect could not certainly produce the higher satisfaction. There is a long history in the traditional therapy of meridians and acupoints, and the meridian regimen and meridian therapy have been recommended by people in the modern times. Acupuncture analgesia guided by the meridian theory has been applied in the clinical obstetrics, but due to difference in the selection of acupoints, instrument coefficient and different needling techniques, the analgesic effects are also different. Now, acupuncture analgesic method has not been popularized in the clinical application.

Judging from the statistics of the literature in the recent 12 years, the reports on application of Hegu (LI 4), Sanyinjiao (SP 6) and Zusanli (ST 36) for relieving labor pain are utmost. It is clear that those three acupoints have the strong analgesic effect for labor pain[2], and are highly recommended by the medical practitioners because all of them are located on the four limbs and are easy for acupuncture application. But, there are not so many reports on other acupoints selected as major acupoints for relieving labor pain. Therefore, to properly screen the analgesic acupoints by further clinical and experimental study is one of the ideas in the future research. In terms of the needling techniques, the reinforcing technique is often applied to Hegu (LI 4) and the reducing technique is often applied to Sanyinjiao (SP 6) based upon the ancient classics. The rest acupoints are mostly punctured with the even needling technique or with the reinforcing technique or reducing technique by pattern identification in accordance with the body constitution. Those operations are basically standard. But, the reinforcing technique or the reducing technique is often appliedwith different duration. Therefore, in the future trials, it is necessary to set up some study on the operating duration of the reinforcing technique and reducing technique. In the literature, the needles are usually retained for 30 min in EA. In accordance with the reports, EA of 50-100 Hz frequency can inhibit the contractive power of the uterus[8], giving an analgesic effect. The acupuncture effect of relieving labor pain may be related to the release of β-endorphin, the increased concentration of 5-TH in the peripheral blood, and the activation of the endogenous analgesic system, due to the excitement by acupuncture. Some scholars think the descending neural pathways of the brain release β-EP, and the release of β-EP increases the excitement in the effect of periaqueductal gray (PAG) of midbrain aqueduct, activates the endogenous analgesic system. After PAG is activated, it goes upward to inhibit the effect of blood-brain parafascicular nucleus to sense the labor pain[18], and further release enkephalin in the spinal cord by the descending pathways[19], producing the analgesic effect via the transmitting channel of labor pain through the ascending pathway of the posterior horn cells and by closure of the pain gate. Acupuncture increases the central 5-HT concentration, and the physiological compensatory system exists between 5-HT and opioid peptide. The increased content of opioid peptide can compensate insufficiency of 5-HT content and increase the analgesic effect for labor pain[20].

In summary, acupuncture analgesia for labor pain is safe, effective and low in cost and is appropriate for popularization for clinical obstetrics. But, there is no standard program for acupuncture analgesia for labor pain, leading to differences in the selection of acupoints, needling techniques and instrument coefficient, and differences in conclusion and less basic studies. To standardize the program of acupuncture analgesia for labor pain by clinical and experimental study for its extensive clinical application is a key task in the future.

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Translator: Huang Guo-qi

R246.3

A

Date: November 10, 2012

Author: Liu Xiao-hui, grade 2010 master degree candidate. E-mail: 715390311@qq.com

Yi Wei, professor, doctorial supervisor. E-mail: 1050031893@qq.com